Trump’s wall won’t work

A truck drives near the Mexico-US border fence, on the Mexican side, separating the towns of Anapra, Mexico and Sunland Park, New Mexico, Wednesday, Jan. 25, 2017. U.S. President Donald Trump will direct the Homeland Security Department to start building a wall at the Mexican border. (AP Photo/Christian Torres)

Photo: Christian Torres, Associated Press

San Francisco is about to feel the brunt of Donald Trump’s presidency. He’s following through on his racially charged obsession with illegal immigration by spending billions on a wall along the Mexican border and cracking down on sanctuary city policies that safeguard undocumented but otherwise law-abiding immigrants.

This city is among hundreds across the country and 40 within California with regulations that bar cooperating with federal immigration enforcers. The details and deadlines for ending these policies remain hazy, but the White House intent is unmistakable.

Trump is elevating demagoguery above effective policy. It’s payback to states and localities where voters didn’t support him. It’s the bluntest possible response to the need for immigration reform.

The president’s stance drew a quick and appropriate rebuff from Mayor Ed Lee. “We’re still a sanctuary city,’’ he said, indicating the city won’t swerve from its path.

With the wall, Trump is initiating a process that won’t likely produce his hoped-for results. He’s once again promising that the barrier will be paid for by Mexico, though that country’s leaders have repeatedly refused to accept such a bill. While borders must be protected, pouring billions into a 2,000-mile fence, high-tech sensors, detention lock-ups and law enforcement personnel may never seal off the map as Trump fervently believes. At best, it’s a partial answer to the complicated, ever-changing challenge of immigration control and security.

His crusade against the sanctuary city movement is another fight he can’t win. Cities across the country have adopted safe-harbor policies to protect law-abiding immigrants who’ve put down roots and established lives in defiance of this country’s restrictive and haphazard laws. The sanctuary protections encourage immigrants who are victims or witnesses of crime to cooperate with local law enforcement.

In focusing on sanctuary cities, Trump is threatening to cut off federal money, though the amount and timetable aren’t clear. He’s taking aim at a roster of cities large and small that includes Los Angeles and Chicago, not just the liberal stronghold of San Francisco.

Cities hosting this population must be resolute in protecting it as a matter of both humanity and public safety.